This invention relates generally to medical catheters and, more particularly, to a Judkins-type angiographic catheter which is equipped to measure coronary blood flow velocity, and a method of using such a catheter.
Judkins-type catheters are commonly used by cardiologists to make diagnostic angiograms of the heart and surrounding arteries. However, this type of catheter is not capable of measuring the velocity of coronary blood flow. For this type of measurement, intracoronary angiographic catheters with Doppler crystals have heretofore been used. One such catheter in common use, sometimes referred to as a 2.5 F intracoronary catheter, consists of an inner tube having a Doppler crystal at its distal end or tip, and an outer guide tube surrounding the inner tube to form an annular space between the two tubes through which X-ray contrast media may be delivered to the heart for the purpose of angiographic diagnosis. In use, the catheter is advanced along a guidewire previously inserted into a coronary artery, until the catheter assumes a position wherein the Doppler crystal at the tip of the inner tube is precisely located relative to the artery. While the use of the guidewire insures precise positioning of the crystal for proper measurement of blood flow velocity, manipulation of the guidewire inside the artery requires a high degree of skill and involves some risk of damaging the walls of the artery. Moreover, angiograms taken using this type of catheter are often less than satisfactory due to unfavorable concentrations of X-ray contrast media delivered through the annular space between the two tubes.
Another type of intravascular catheter used to measure coronary blood flow velocity is sometimes referred to as a Sones-Doppler catheter, which is a relatively straight stiff catheter with an annular Doppler crystal at its tip. Sones-type catheters are illustrated on page 142 of Coronary Arteriography and Angioplasty, by Spencer King, M.D., incorporated herein by reference. However, Sones-type catheters are difficult to manipulate, and require a high degree of specialized training to use. For example, to place a Sones-type catheter in the left coronary artery requires careful manipulation of the catheter; the catheter is actually manipulated by impinging it against the coronary cusp. This is illustrated on pages 151 and 153 of Coronary Arteriography and Angioplasty. Moreover, the stiffness of the catheter, and the hard sharp tip formed by the Doppler crystal, present a risk of internal injuries.
Because of the risks associated with these prior catheterization procedures for measuring the velocity of coronary blood flow, these procedures are not generally justified for patients without coronary artery disease. In contrast with these prior Doppler-equipped catheter, Judkins-type diagnostic catheters are much easier to manipulate, and they present less risk of injury to the patient. The use of these catheters, for example the Judkins-type catheters is relatively safer and more familiar to most cardiologists. However, none of these diagnostic catheters is equipped to measure blood flow velocities in coronary arteries.